I don't support the notion of buying shorter oars and getting extenders. I added extenders to my first setup, which had too short of oars. They are extremely heavy (2' total aluminum length), clunky, and switching back and forth between 1' difference is a heck of a lot. Perhaps if they came out with 6" extenders, but they'd still be heavy beasts out at the end of your shaft.
I use 10's on a 14' raft, and generally like longer oars. I also sit on the cooler which puts me higher which pushes me towards longer oars for properly reaching the water. I keep the handles close together and my towers are on the outer rail of a double-rail frame, which makes it more manageable to have longer oars.
Keep in mind you can cut oars shorter, but can't lengthen them. That's a bit of a hassle, but I erred on the side of longer oars when I bought our latest raft, risking that I knew I could always cut them off. I never did do that, and stayed with the 10' length.
I am a river, babe - I've got plenty of time, I don't know where I'm going, I'm just following the lines..... - "We are water" by Shaye